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pressure oscillations in moving mesh cases

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Old   April 29, 2009, 08:52
Default pressure oscillations in moving mesh cases
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David Hora
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Hi all

I'm trying to simulate a pump (inlet casing, rotating impeller, diffuser and volute) with OpenFOAM-1.5-dev. The four domains are connected with GGI interfaces. The turbDyMFoam solver is used as it is a transient simulation. The forces acting on the hub, shroud and blades are monitored with the forces functionObject. Unfortunately the pressure forces oscillate with each time step. The attached image shows the pressure forces in y-direction. Rotation axis is the z-axis.


I could reproduce this behaviour in the icoDyMFoam tutorial cases mixerGgi and mixer2D. I tried to use different ddt-Schemes (Euler, backward, CrankNicholson) and tolerances without any improvement. Are there any possibilities to reduce the oscillations?


Thanks in advance

David
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Old   April 29, 2009, 15:07
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Louis Gagnon
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Hi David,

I assume that by oscillations you mean the noise and not the sinusoidal oscillation of the signal? If so, I've read that using a smaller timestep might reduce the noise.

cheers,

-Louis
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Old   April 30, 2009, 03:24
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David Hora
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Hi Louis

Yes, the noise is the problem. Unfortunately, reducing the time step doesn't improve the results.

Regards

David
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Old   July 29, 2009, 03:44
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Mark Couwenberg
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Hello,

try to use some relaxation on p (or pd). First check whether relaxationFactors are implemented in the solver you use, otherwise you can easily implement them yourself.

Succes,

Mark
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Old   April 25, 2011, 11:15
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Sung-Eun Kim
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Quote:
Originally Posted by david View Post
Hi Louis

Yes, the noise is the problem. Unfortunately, reducing the time step doesn't improve the results.

Regards

David
David,

I have similar prroblems you've had. With
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Old   April 25, 2011, 11:16
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Quote:
Originally Posted by david View Post
Hi all

I'm trying to simulate a pump (inlet casing, rotating impeller, diffuser and volute) with OpenFOAM-1.5-dev. The four domains are connected with GGI interfaces. The turbDyMFoam solver is used as it is a transient simulation. The forces acting on the hub, shroud and blades are monitored with the forces functionObject. Unfortunately the pressure forces oscillate with each time step. The attached image shows the pressure forces in y-direction. Rotation axis is the z-axis.


I could reproduce this behaviour in the icoDyMFoam tutorial cases mixerGgi and mixer2D. I tried to use different ddt-Schemes (Euler, backward, CrankNicholson) and tolerances without any improvement. Are there any possibilities to reduce the oscillations?


Thanks in advance

David
=================================
Hi David,

I am having a similar "noise" problem. Were you able to resolve your problem?
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